Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
thuc va » thuc vat, thuc dan, thuc day
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
ky lang » ky nang, ky dang, ky tang
ha hoi » hoa hoi, ha noi, va hoi
va dan » ca dan, va dao, va dau
va cau » van cau, va cac, va dau
va chu » va che, va chi
va nam » van nam, ha nam, va nay

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky lang ((ha hoi) OR (xa hoi)). hieu va nam thuc va dan ((va cau) OR (va chu)) tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky lang ((ha hoi) OR (xa hoi)). hieu va nam thuc va dan ((va cau) or (va chu)) tre~".
• Adding a wildcard symbol may retrieve word variants: toc sach ky lang ((ha hoi) OR (xa hoi)). hieu va nam thuc va dan ((va cau) or (va chu)) tre*.